package org.apache.lucene.search;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.util.BitSet;

import org.apache.lucene.index.IndexReader;

/**
 * Provides caching of {@link Filter}s themselves on the remote end of an RMI
 * connection. The cache is keyed on Filter's hashCode(), so if it sees the same
 * filter twice it will reuse the original version. <p/> NOTE: This does NOT
 * cache the Filter bits, but rather the Filter itself. Thus, this works
 * hand-in-hand with {@link CachingWrapperFilter} to keep both file Filter cache
 * and the Filter bits on the remote end, close to the searcher. <p/> Usage:
 * <p/> To cache a result you must do something like RemoteCachingWrapperFilter
 * f = new RemoteCachingWrapperFilter(new CachingWrapperFilter(myFilter)); <p/>
 * 
 * @author Matt Ericson
 */
public class RemoteCachingWrapperFilter extends Filter {
	protected Filter filter;

	public RemoteCachingWrapperFilter(Filter filter) {
		this.filter = filter;
	}

	/**
	 * Uses the {@link FilterManager} to keep the cache for a filter on the
	 * searcher side of a remote connection.
	 * 
	 * @param reader
	 *            the index reader for the Filter
	 * @return the bitset
	 */
	public BitSet bits(IndexReader reader) throws IOException {
		Filter cachedFilter = FilterManager.getInstance().getFilter(filter);
		return cachedFilter.bits(reader);
	}
}
